JPH0773496A - Semiconductor laser beam device - Google Patents

Abstract

PURPOSE:To hold the light quantity of laser beam to a prescribed fixed value precisely by arranging a second detection means in the vicinity of an optical recording medium, detecting the light quantity of the semiconductor laser beam and adjusting a control means based on the detected result. CONSTITUTION:An optical pickup is moved to a position B outside an optical disk at the initial time of driving such as the time when power source is applied, etc., and a beam is cast on a second detector 21 by reproducing power. An obtained signal is inputted to a gain variable amplifier 13 through a second I/V converter 22 and a controller 23, and a gain is varied so that the reproducing power on a light receiving surface becomes a required value. After the gain is adjusted, the pickup is moved to the inside, and the beam is cast on the optical disk 5. By a comparator 14, the semiconductor laser 1 is driven according to the compared result of the output voltage of the gain variable amplifier 13 with a prescribed reference voltage. Since the reproducing power is controlled after the gain is adjusted according to the reproducing power, the required laser light quantity is obtained always even when a semiconductor laser characteristic and the use efficiency of an optical system change with time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used for recording and reproducing on an optical recording medium such as an optical disk.

[0002]

2. Description of the Related Art In recent years, in optical disk devices for recording and reproducing optical recording media such as optical disks, semiconductor lasers are generally used as a light source because of the high output and low cost of semiconductor lasers. It has become to.

A conventionally used semiconductor laser device will be specifically described with reference to FIG. In the figure, reference numeral 1 denotes a semiconductor laser, and a beam emitted from the semiconductor laser 1 is collimated by a collimator lens 2 to form a parallel beam,
Through the objective lens 4 and focused on the recording surface 6 of the optical disc 5. The beam reflected by the optical disk 5 is reflected by the beam splitter 3, passes through the detection lens 7, and enters the parallel plate 8. The beam reflected by the parallel plate 8 is focused on the tracking signal detector 9, and the passing beam is focused on the focus signal detector 10. The signals detected by these signal detectors 9 and 10 are used for tracking control and focus control, respectively.

A part of the light emitted from the semiconductor laser 1 is
It is separated by the beam splitter 3 and is incident on the photodetector 11 such as a photodiode. The output signal from the photodetector 11 is converted into a voltage value by the current-voltage converter (I / V) 12 and is input to the gain variable amplifier 13 whose gain is appropriately adjusted. The comparator 14 compares the output voltage of the variable gain amplifier 13 with a predetermined reference voltage 15, and drives the driving means 16 according to the comparison result. The specific circuit configuration of the photodetector 11, current-voltage converter 12, variable gain amplifier 13, and comparator 14 is shown in FIG.

The adjustment of the variable gain amplifier 13 is
The reproduction power on the surface of the optical disc 5 is adjusted to be, for example, 1 mW. The semiconductor laser 1, beam splitter 3, photodetector 11, current-voltage converter 12, variable gain amplifier 13, comparator 14, reference voltage 15, driving means 1
A control loop is formed at 6, and the emitted light of the semiconductor laser 1 is controlled to be constant based on the reference voltage.

[0006] In addition, for example, the one disclosed in Japanese Patent Laid-Open No. 4-69824 is proposed. That is, a part of the light emitted from the front surface of the semiconductor laser is separated and converted into an electric signal, the low frequency component and the high frequency component of this electric signal are amplified and added, and the added signal and the reference signal are compared and the semiconductor signal is compared. It controls the output of the laser.

[0007]

However, the adjustment of the variable gain amplifier or the like in the above-mentioned conventional semiconductor laser device is provided with a light quantity measuring device at the optical disk surface position without adjusting the optical disk, so that the variable gain amplifier is adjusted. This is performed only once when the device is assembled, and the reproduction power cannot be controlled to be constant with respect to changes over time in the characteristics of the semiconductor laser and the utilization efficiency of the optical system. If the reproduction power fluctuates due to such changes over time, information recording / reproduction may not be performed normally, or the reliability of information may deteriorate.

The present invention provides a semiconductor laser device which eliminates the power adjustment of the semiconductor laser when assembling the optical disk device and can always obtain a constant power even if the semiconductor laser characteristics and the utilization efficiency of the optical system change with time. The purpose is to do.

[0009]

The present invention has been made in order to achieve the above-mentioned object, and comprises a semiconductor laser and a semiconductor laser driving means for driving the semiconductor laser,
In a semiconductor laser device used for recording and reproducing on an optical recording medium, an optical system for separating a part of emitted light of the semiconductor laser, and first detecting means for detecting a light amount of the separated semiconductor laser. A control means for controlling the light quantity of the separated semiconductor laser to be constant based on the result of the first detecting means; and a light quantity of the semiconductor laser arranged near the optical recording medium. The semiconductor laser is characterized by comprising two detection means and an adjustment means for adjusting the light quantity of the semiconductor laser controlled by the control means to a desired value based on the detection result of the second detection means. It is a device. Further, the control means is
The adjusting means has a gain variable amplifier for amplifying the output signal from the first detecting means, and a comparing means for comparing the signal amplified by the gain variable amplifier with a predetermined reference signal, and the adjusting means. , The gain of the variable gain amplifier is changed based on the output signal of the second detecting means. The control means has a comparison means for comparing the output signal from the first detection means with a reference signal, and the adjustment means changes the reference signal based on the output signal of the second detection means. . The adjusting means operates at the time of initializing the optical disk device.

[0010]

According to the present invention, the light amount of the semiconductor laser is detected by the second detecting means arranged near the optical recording medium, and the control means is adjusted based on the detection result. Therefore, the light quantity of the semiconductor laser is accurately kept constant at a predetermined value by the control means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is an explanatory view showing a first embodiment of the present invention, in which 1 is a semiconductor laser, and a beam emitted from this semiconductor laser 1 is collimated by a collimator lens 2 and passes through a beam splitter 3. The objective lens 4 focuses on the recording surface 6 of the optical disc 5. Optical disc 5
The beam reflected by is reflected by the beam splitter 3, passes through the detection lens 7, and enters the parallel plate 8. The beam reflected by the parallel plate 8 is focused on the tracking signal detector 9, and the passing beam is focused on the focus signal detector 10. The signals detected by these signal detectors 9 and 10 are used for tracking control and focus control, respectively, and they form an optical pickup.

The semiconductor laser device of the present embodiment has a first photodetector 11 including a photodiode or the like for detecting a part of the emitted light of the semiconductor laser 1 separated by the beam splitter 3. The first current-voltage converter (I / V) 12 for converting the electric signal (current) obtained from the first photodetector 11 into a voltage, and the first current-voltage converter 12 A gain variable amplifier 13 that amplifies an output signal (voltage value), a comparator 14 that compares the output signal of the gain variable amplifier 13 and a reference voltage 15, and the semiconductor laser 1 is driven based on the output of the comparator 14. The driving means 16 is provided, and these constitute a control means. The specific circuit configuration of these is the same as that of the conventional technique (see FIG. 4).

On the other hand, a second detector 21 for detecting the light quantity of the semiconductor laser 1 arranged near the optical disk 5, that is, outside the outermost circumference of the optical disk and at substantially the same height as the surface of the optical disk 5, is provided. Have. And this second
A second current-voltage converter (I / V) 22 for converting the output signal (current value) of the second detector 21 into a voltage.
The controller 23 that adjusts the gain of the variable gain amplifier 13 based on the output signal (voltage value) of the current-voltage converter 22 is used as the adjusting means.

Next, the operation of this apparatus will be described. At the time of drive initialization such as power-on of the optical disk drive, the optical pickup is moved further outside the outermost peripheral position of the optical disk (position B), and the second detector 21
A beam is emitted at the reproduction power. This second detector 2
The signal obtained from 1 is converted into a voltage value by the second current-voltage converter 22, and the voltage value is input to the controller 23. Since the controller 23 knows the reproduction power on the light receiving surface of the second detector 21 from the input voltage value,
The gain of the variable gain amplifier 13 is changed so that this voltage value becomes a desired value (that is, the reproduction power becomes a desired value (for example, 1 mw) on the light receiving surface). As the variable gain amplifier 13, it is preferable to use a general voltage control amplifier (VCA) whose gain can be changed with respect to the control voltage output from the controller 23.

After adjusting the gain of the variable gain amplifier 13 according to the reproduction power of the second detector 21 as described above, the optical pickup is moved inward from the position A so that the optical disk 5 can be irradiated with the beam. However, since the reproducing power is controlled by the control means, a constant reproducing power can be obtained.

That is, a part of the emitted light of the semiconductor laser 1 is separated by the beam splitter 3 and is incident on the first photodetector 11 such as a photodiode. The output signal from the first photodetector 11 is the first current-voltage converter 1
It is converted into a voltage value by 2 and input to the variable gain amplifier 13. The comparator 14 compares the output voltage of the variable gain amplifier 13 adjusted as described above with a predetermined reference voltage 15, and drives the semiconductor laser 1 according to the comparison result.

Therefore, since the reproduction power is controlled after the gain of the gain variable amplifier 13 is adjusted according to the reproduction power in the second photodetector 21, the semiconductor laser characteristics and the optical system can be used over time. Even if the efficiency changes, the desired amount of laser light can always be obtained.

Next, a second embodiment will be described with reference to FIG. The semiconductor laser device of the present embodiment includes a first photodetector 1 including a photodiode or the like for detecting a part of the emitted light of the semiconductor laser 1 separated by the beam splitter 3.
Has 1. Then, a first current-voltage converter 12 for converting the electric signal (current) obtained from the first photodetector 11 into a voltage, and an output signal of the first current-voltage converter 12 will be described later. It has a comparator 14 for comparing with a reference voltage created by the controller 23, and a driving means 16 for driving the semiconductor laser 1 based on the output of this comparator 14, and these constitute a control means.

On the other hand, the second detector 21 for detecting the light quantity of the semiconductor laser 1 arranged near the optical disc 5, that is, outside the outermost periphery of the optical disc and at substantially the same height as the surface of the optical disc 5. Have. Then, a second current-voltage converter 22 for converting the output signal (current value) of the second second detector 21 into a voltage, the second current-
The controller 23 has a controller 23 that creates a reference voltage to be input to the comparator 14 based on the output signal (voltage value) of the voltage converter 22, and constitutes the adjusting means.

Next, the operation of this apparatus will be described. Similar to the first embodiment, when the drive is initialized such as when the optical disk drive is powered on, the optical pickup is moved further outside the outermost peripheral position of the optical disc (position B).
The second detector 21 is irradiated with a beam with reproduction power. The signal obtained from the second detector 21 is converted into a voltage value by the second current-voltage converter 22, and the voltage value is input to the controller 23. On the other hand, the output signal from the first photodetector 11 is converted into a voltage value by the first current-voltage converter 12 and input to the comparator 14. The controller 23 knows the reproducing power on the light receiving surface of the second detector 21 from the input voltage value, so that this voltage value becomes a desired value (that is, the reproducing power on the light receiving surface is a desired value). The reference voltage input to the comparator 14 is variably adjusted (eg, 1 mw).

After the reference voltage input to the comparator 14 is adjusted according to the reproduction power of the second detector 20 as described above, the optical pickup can irradiate the optical disk 5 with a beam as in the first embodiment. As described above, the reproducing power is moved inward from the position A, and the control means controls the reproducing power.
A constant reproduction power can be obtained.

[0022]

As described above, according to the present invention, the light quantity of the semiconductor laser controlled by the control means based on the detection result of the second detection means arranged near the optical recording medium is set to a desired value. Since it is configured to adjust (gain adjustment of the variable gain amplifier or adjustment of the reference signal input to the comparison means), it is not necessary to adjust the laser light when assembling the drive, and adjustment can be performed after the assembly.
It is possible to always adjust to a desired light amount. Further, the above adjustment can be performed at the time of initializing the drive, etc., so that the desired light amount can be constantly adjusted even if the semiconductor laser characteristics or the utilization efficiency of the optical system changes with time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a conventional example.

FIG. 4 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 1 Semiconductor Laser 2 Collimator Lens 3 Bim Splitter 4 Objective Lens 5 Optical Disc 6 Recording Surface 7 Detection Lens 8 Parallel Plate 9 Tracking Signal Detector 10 Focus Signal Detector 11 First Detector 12 First Current-Voltage Converter 13 Gain Variable amplifier 14 Comparator 15 Reference voltage 16 Driving means 21 Second detector 22 Second current-voltage converter 23 Controller

Claims (4)

[Claims] 1. A semiconductor laser device comprising a semiconductor laser and a semiconductor laser driving means for driving the semiconductor laser, which is used for recording and reproducing on an optical recording medium, wherein a part of emitted light of the semiconductor laser is An optical system for separating, a first detecting means for detecting the light quantity of the separated semiconductor laser, and control so that the light quantity of the separated semiconductor laser becomes constant based on the result of the first detecting means. Control means, second detection means for detecting the light quantity of the semiconductor laser arranged near the optical recording medium, and light quantity of the semiconductor laser controlled by the control means based on the detection result of the second detection means. Is a desired value, and a semiconductor laser device. 2. The control means compares the gain variable amplifier for amplifying the output signal from the first detection means with a signal amplified by the gain variable amplifier and a predetermined reference signal. And adjusting means,
2. The semiconductor laser device according to claim 1, wherein the gain of the variable gain amplifier is changed based on the output signal of the second detecting means. 3. The control means has a comparing means for comparing an output signal from the first detecting means with a reference signal, and the adjusting means has the reference signal based on the output signal of the second detecting means. 2. The semiconductor laser device according to claim 1, wherein 4. The semiconductor laser device according to claim 1, wherein the adjusting means operates during initialization of the optical disk device.